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BMW E46 3-Series Rear Shock Reinforcement Plate Install, Convertible, Etc. – How To

January 2, 2013

Installing the rear shock absorber mounting reinforcement plates is a great idea for any 3-series or Z3 models from 1984 through 2005.  This includes:

E30: 3-series 84-91 (318i, 318is, 318ic, 325e, 325es, 325i, 325is, 325ix, 326ic, M3) plus 92 convertibles

E36: 3-series 92-98 (318i, 318is, 318ic, 323is, 323ic, 325i, 325is, 325ic, 328i, 328is, 328ic, M3) plus 99 convertibles and coupes

E36/7, E36/8: Z3 coupe & roadster (1.9, 2.3, 2.5, 2.8, 3.0, M)

E46: 3-series 99-05 (323i, 323ci, 323cic, 325i, 325ci, 325cic, 325xi, 328i, 328ci, 330i, 330ci, 330cic, 330xi, M3) plus 99 convertibles and coupes

The reinforcing plates help to distribute the stresses that are transferred from the upper shock mounts to the sheetmetal shock tower area.  Historically, we have seen the sheetmetal crack around the holes for the mount studs.  This can actually lead to a complete failure of the sheetmetal shock mounting area.

On most models, the installation is very easy and straight forward.  You simply drop the reinforcing plate over the mounts’ studs before threading on the nuts.  Some models do have unique issues, however.  One such model is the E46 chassis convertibles.  The “folding top compartment” (the well that the top folds down into) prevents direct access to the tops of the shock mounts.  Follow below as one of our customers, Larry, shows how he installed the plates on his 2001 330i convertible.  Larry’s original post is on the BMW forum; .

3-series rear shock mount reinforcement plates:

Larry’s DIY:

You can install the rear shock tower reinforcement plates PN. 51 71 8 413 359 by doing the following.

1. Remove the Torx screws to remove the “Folding Top Compartment”. All screws are in the top storage compartment area, none in the trunk- 17 screws, T30 Torx. Pull up on the front part of compartment.  It just snaps up.  There is a connector on the passenger side that must be disconnected after you raise the compartment up a few inches. Slide the compartment into the trunk.

2. Pull the trunk liner back from around shock tower area and slide the Reinforcement Plates in as shown. On both sides (once they are over shock tower) you will need to raise the outboard side of the plate slightly to get the inboard side of the plate to slip under the convertible top bracket – then the plate will drop right into place on top of the tower. Passenger side plate slides in from the front…. the drivers side plate slides in from the rear. It’s also recommended the chambered edge of the hole in the plate face down.

3. Unlike the coupes, sedans, etc. where you would raise the shock assembly into the tower and then drop the plate over the 2 shock mount studs I’m just about positive you won’t be able to install these plates in the convertible in that way…. because of the convertible top mounting hardware, brackets, etc. around the shock towers.  These plates have to be slid in from the side and then dropped down over the shock tower as described above and then the shock assembly raised into place (the shock mounts must be removed before placing the plates into position). The top of the shock and mount studs would be in the way if in the installed position. The plates aren’t going anywhere once the are dropped onto the top of the tower.

* All photos by originating author

  1. Frank F. permalink

    Nice DIY! Looks like you have a nice E46 convertible there. Did you have to remove any of the roof components for this DIY?

    • Otto permalink

      Larry notes that you do not remove the convertible top. In order to work in the area required, open or close the top to the point where the rear section is lifted from the rear deck and then turn off the ignition (assuming a power top) to stop it in this position. The top will slowly lower due to the hydraulic system leaking down. Larry recommends placing something under the lifted rear section to keep it from falling as you perform the work.

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